I went from an FR TDI to my Petrol Cupra, and although the TDI felt faster, it clearly wasn't when you try taking on a Fiesta ST for example. I've found that the Cupra petrol engine has more usefull power, because unlike a diesel, power is spread much further across the rev range, and builds the higher the revs go. Diesels give it all low down, and you run out of steam as you approach 4k on the rev guage!
Depends on your driving style tho - some like the kick in the back torque of the diesel, where as those with a heavy right foot like me will properly have a driving style more suited to a petrol.
Driving the petrol Cupra the way Seat intended will empty your wallet pretty swiftly, but things that are fun always cost more - and I don't care much for saving the trees just yet! The derv will save more on fuel and tax - but is also quite a bit more expensive to buy.
Try and drive both from a dealer - then make a decision
